I remember walking through farmers markets with my grandparents as a kid. Seeing the endless rows of fruits, vegetables, and anything else you could ask for. Holding my grandpa’s hand as we walked up and down the rows, shopping for what looked best.

Each item of produce we purchased was carefully examined for ripeness and quality. Turned carefully over in my Grandma or Grandpa’s hands. Inspecting it for blemishes or color or general ripeness. As a kid, the complexity of determining quality and ripeness never ceased to amaze me.

How can we tell if something is ripe or will taste good if we aren’t able to taste it first? For my grandparents, it meant carefully handling or tapping on some produce items, while others they would smell for sweetness. In my family, each item had its own perplexing sequence of steps to determine quality. What about the farmers of these produce items? How do they check an entire field for quality or ripeness?

Produce growers around the world have a plethora of tools and lifetimes of experience to accomplish their noble task of feeding the population. As technology has continued to advance, so too have the tools growers use to determine quality. One such tool is known as a refractometer.

These easily accessible and widely used devices measure the value of soluble solids in a fruit or vegetable. A refractometer typically reports these levels as °Brix or °Bx. The measurements are used by growers and processors to gauge plant health, schedule harvest, modify irrigation timings, fertility needs, and a host of other factors.

At the simplest level however, °Brix is a measure of potential sweetness of fruit and vegetable samples. One degree Brix is equal to one gram of sucrose per 100 grams of solution.

How does this device determine how sweet a fruit or vegetable is? Think back to a time in your childhood spent swimming. I can vividly remember reaching down into the pool to grab items off the bottom as part of a game.

The strange part is that the items weren’t ever where you thought they were, or it looked as though your arm had changed direction under water. This is due to a phenomenon called refraction—the bending of light as it passes through another medium.

Refractometers utilize this physics principle to produce a °Brix reading by measuring the degree at which light is bent as it passes through the sample solution. The higher the soluble solids in the sample—or in other words, the more dissolved sugar there is—the greater the degree of refraction or bending of light.

The refractometer then interprets that degree of light refraction to produce a reading. The ideal °Brix level varies from crop to crop and is based on the intended use of the crop, as well as potential consumer preference.

Portable refractometers are valuable tools used by specialty crop producers all around the world. A relatively simple tool, its value lies in its portability and ease of use.

brix refractometer
Once a solution is created using samples from the crop, it is placed on the window of the refractometer using a pipette.

The window covering is then closed and is held up to a light source (though some refractometers have self-contained lights) and is examined to find the °Brix. Here, Miller Chemical California Territory Manager Sal Ruedas is evaluating the reading.

Looking through the eyepiece of the refractometer after a light source is introduced will give this view. For this particular sample, the reading is approximately 17 °Brix

Reminiscing back to my time in the farmer’s market with my grandparents now, it still makes me smile. Their methods seemed so complex and interesting and scientific to watch as a young child. Even more amazing is that the methods they used always seemed to work!

Fast forward nearly three decades, and as my knowledge of agriculture has grown and technology has advanced, I cannot imagine the average farmer today handling, smelling, and tapping the produce as their only test for crop quality and ripeness. This does still occur, and it can be incredibly effective, as my grandparents taught me as a kid.

With the availability and accessibility of tools such as the portable refractometer however, growers today are able to manage their crop to an even higher level of quality than ever before. That said though, I admit I am still excited to teach my son those produce selection lessons I learned from my grandparents all those years ago.

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